UK prime ministers do not legally need to consult Parliament before launching military action, although they have done so since the 2003 invasion of Iraq.

Mrs May is due to give a Commons statement on Monday before facing questions from MPs.

She is also expected to ask the Speaker for permission to hold an emergency debate in Parliament on the issue of Syria.

Media captionPrimary purpose of Syria air strikes was “to say no to the use of barbaric weapons”, says Boris Johnson

BBC political correspondent Ben Wright said if approved it would be up to the opposition parties to decide if they wanted a vote at the end of the debate.

Any vote would be “largely symbolic” and would mainly just acknowledge that Parliament has had its say rather than give MPs the chance to formally approve or reject the air strikes themselves.

Theresa May’s decision to authorise action without MPs’ backing has been criticised by Labour leader Jeremy Corbyn, who said she could “easily” have recalled Parliament or delayed her decision until MPs returned to Westminster from the Easter recess.

Mr Corbyn called for a new War Powers Act “so governments do get held accountable to Parliament for what they do in our name”.

Media captionCorbyn: Trump should pick up the phone to Putin

Labour’s shadow attorney general Shami Chakrabarti told BBC Breakfast: “I have concerns about the legality of the strikes on the basis of the tests that government has set itself.

“In particular, it seems far from clear to me that there was overwhelming evidence widely accepted by the international community that this had to happen so urgently and also that there was no practical alternative – even when the chemical weapons inspectors were on their way into Syria.”

The calls by Mr Corbyn for a War Powers Act were dismissed by cabinet minister David Lidington, who told ITV there were “no plans” to change the law.

“Governments have to bear in mind the need to be able to act swiftly and flexibly and to protect the safety of our servicemen and women,” he added.

The Scottish National Party said it would table a motion for an emergency debate to try to get MPs a vote on whether they backed the military action.

Mr Corbyn, who has warned of an escalation in a “proxy war” between the US and Russia, said he would only consider backing intervention in Syria with the support of the United Nations.

“If we could get to a process in the UN where you get to a ceasefire, you get to a political solution, you then may well get to a situation where there could be a UN force established to enforce that ceasefire,” he told the BBC’s Andrew Marr Show on Sunday.

“That surely would save a lot of lives.”

But the Conservatives said he knew “full well” that Russia would veto such a move.